The present invention relates to a light source module with two wavelengths which emits a light beam with two wavelengths.
As technologies in optical disk fields advance, DVDs are developed, which have a size 6 to 7 times larger than a capacity of CD for exclusive use of audio, an optical disk for use as a computer supplementary memory, or present CD. Though an optical pickup for reading the DVD developed together with the DVD presently is interchangeable with CD, the optical pickup for reading the DVD has no interchangeability with CD-R(Recordable) disk, which is a WORM (Write Once Read Many) type having a reflexion ratio higher at 780 nm wavelength and lower at 650 nm wavelength, because a laser beam source used in the optical pickup has a wavelength of 650 nm. Therefore, the interchangeability with a writable CD(CD-R), of which market expands rapidly, is an important matter for the optical pickups for DVD-ROM, or DVD-RAM. As shown in FIG. 1, a method available presently is use of two LD(Laser Diode) each with a wavelength of 650 mm or 780 mm for switching to a disk desired to read.
Referring to FIG. 1, a related art optical pickup is provided with an LD 1 of 650 nm, LD 4 of 780 nm, a first collimator 2 for the LD of 650 nm, a second collimator 5 for the LD of 780 nm, a first beam splitter 3 for directing a laser beam from the 780 nm LD toward a 45 degree reflection mirror and passing a laser beam from the 650 nm LD, the 45 degree reflection mirror 7, an objective lens 8, a second beam splitter 6 for directing a laser beam reflected at a disk toward a photodetector 12, a focusing lens 9 for focusing a beam onto the photodetector 12, and the photodetector 12 for generating an objective lens servo signal and an information signal recorded on the optical disk.
Referring to FIG. 1, the operation of the related art optical pickup will be explained. When a DVD is read, the 780 nm LD 4 is turned off, and only the 650 nm LD 1 is operative, to emit a laser beam, which is collimated by the first collimator 2, passes through the first beam splitter 3 and the second beam splitter 6 in succession, is directed to the objective lens 8 by the 45 degree reflection mirror 7. The beam incident to the objective lens 8 is focused onto the DVD 10 by the objective lens 8, and reflected at the DVD 10 to travel a beam path in a reverse direction, a portion of which is focused onto the photodetector 12 by the second beam splitter 6. As a laser beam is incident to the photodetector 12, the photodetector 12 provides information signal recorded on a objective lens servo and the disk. In reading a CD or a CD-R, the light source is changed over from 650 nm LD to 780 nm LD, and the information is read under the same principle. Referring to FIG. 1, when the CD or CD-R are read, an effective diameter of the beam incident to the objective lens is smaller than the same when DVD is read, because, when the 780 LD is used, it is required to reduce an effective diameter of the beam incident to the objective lens to form a spot of approx. 1xcx9c1.2 xcexcm since the objective lens is provided exclusively for DVD.
The 780 nm LD required to provide additionally when the aforementioned optical pickup designed for reading DVD and CD group disk is to read the CD-R causes a cost high, complicate to fabricate the optical pickup, and increases the size.
Accordingly, the present invention is directed to a light source module with two wavelengths that substantially obviates one or more of the problems due to limitations and disadvantages of the related art.
An object of the present invention is to provide a light source module with two wavelengths, in which light sources with two wavelengths are integrated into one module, to provide a light source module with two wavelengths, which is easy to fabricate and minimize a bulk.
Another object of the present invention is to provide a light source with two wavelengths which can emit light beams of different wavelengths using a submount which can be passive aligned.
Additional features and advantages of the invention will be set forth in the description which follows, and in part will be apparent from the description, or may be learned by practice of the invention. The objectives and other advantages of the invention will be realized and attained by the structure particularly pointed out in the written description and claims hereof as well as the appended drawings.
To achieve these and other advantages and in accordance with the purpose of the present invention, as embodied and broadly described, the light source module with two wavelengths includes a first and a second laser diodes each for emitting a laser beam with a wavelength different from each other, and a submount formed between the first and second laser diodes having a vertical mirror surface vertical to bonding surfaces of the first and second laser diodes for reflecting laser beams from the first and second laser diodes in a same direction.
The vertical mirror surface is either a flat or parabolic mirror disposed at 45xc2x0 to the laser beams incident thereto.
The light source module further includes a stem for supporting the submount having the vertical mirror surface, and the first and second laser diodes, and a cap fitted with a collimator, the cap formed over the stem for protecting the submount, and the collimator for collimating respective laser beams emitted from the first and second laser diodes and reflected at the vertical mirror surface toward an external optical system.
In other aspect of the present invention, there is provided a light source module with two wavelengths including a first and a second laser diodes each for emitting a laser beam with a wavelength different from each other, a mirror block disposed between the first and second laser diodes and having a vertical mirror surface for reflecting laser beams from the first and second diodes in the same direction, and a submount having a first and a second recesses formed in a fixed depth under the first and second laser diodes and the mirror block for aligning the first and second laser diodes and the mirror block, and a third recess formed in a fixed depth having a mirror surface for re-reflecting the laser beam reflected at the mirror block in a fixed direction.
It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory and are intended to provide further explanation of the invention as claimed.